Fasting and after

I´m going to fast in february.

What is the best fasting for a newbie?

I plan to go back to a low carb high fat diet afterwards since I will already be in ketosis. I´ve been eating that before and I felt great.

I am addicted to coffee and that will stop. I also smoke and that will definatly stop.

So. I guess my question is:

Wich way is the best way? Pure water or what?

How should I restart eating afterwards?

Best regards to you all.